Polyesters are an important class of commercial polymers, being used as molding resins, fibers for industrial and textile use, and films. Therefore, improved processes for producing polyesters are continually sought.
U.S. Pat. No. 3,925,295 describes the preparation of polymer dispersions, including polyesters, by carrying out a condensation polymerization at a temperature of at least 150.degree. C. in an inert liquid medium containing a polymeric emulsifying agent which disperses both the starting material and final polymer, to produce a polymer dispersion in the inert liquid. The polymeric emulsifying agent is an "impurity" in the polyester produced.
U.S. Pat. No. 4,613,664 describes the preparation of polyesters by heating a polymerizable oligomer in a specified inert medium (which may swell the oligomer and/or final polyester). No mention is made of boiling the inert medium to remove the low boiling byproduct of the condensation polymerization.